Constant air flow heat exchanger



AMay 24,- 1.966

w. J. Kil-:'EGAN vCONSTANT AIR FLOW HEAT vEXCHNGER Filed June 14, 1963 2 SheetsSheet 1 INVENTOR, /4// MM J Kas-64N .glp

May 24, 1966 w. J. KEEGAN CONSTANT AIR FLOW HEAT EXCHANGER 2 Sheets-Sheet 2 "Fiied June 14, 1965 .N ru R 04 .4 L E .C VK ,N m W J mn M Z l m Mw w W @M500 2.2224. M m ,M XmmmX Q i 2 l. .I1 lll* United States Patent Office 3,252,509 Patented May 24, 1966 3,252,509 CONSTANT AIR FLOW HEAT EXCHANGER William J. Keegan, Farmington, Mich., assigner to American Radiator &,Standard Sanitary Corporation, New York, N.Y., a corporation of Delaware Filed June 14, 1963, Ser. No. 287,990 3 Claims. (Cl. 165-103) This invention relates to an air conditioning unit, and pa-rticularly to such a unit employing a novel vane element for directing vair through a heat-exchange coil and/or through a by-pass passage within the unit, .to deliver conditioned air from .the unit at a liow rate of improved uniformity.

The problem In air conditioning building structures, such as homes, olhce buildings and the like, it is customary to provide an enclosin-g casing or housing for a heat-exchange coil, either heating or Acooling coil, and,y pass varying amounts of the total air tiow over the coil to -adjust the temperature of the exit air to a desired level. In conditioning air in this manner, of course, it is desirable to have the air flow sub stantially uniform, so that a controlled change of air in the dwelling per unit time can be established for a proper treatment.

However, in the prior art, the -achievement of the constant air flow has not been provided. A typical prior art structure, as evidenced by British Patent 379,663 dated September 1, 1932, utilizes a liat damper plate or bathe to di-rect incoming air through a by-pass passage or heatexchanger or both. However, the 4use of a flat baiie does not compensate for the changing resistance of the heatexchange unit in accordance with varyin-g flow therethrough. Accordingly, depending upon the position of the baille, the volume of air iiowing from the unit will decrease as -a greater amount is passed through the heatexchange unit, thus imposing at full flow the full resistance of the heat exchanger. Concomitantly, full by-pass tiow will be the greatest amountfof ow, because of less resistance.

Accordingly, an important Vstep forward in the art would be provided by a heat-exchange ventilator wherein uniform gas ow is provided even with changing ow through the heat-exchanger.

Accordingly, an important object is to provide an `air conditioning system having improved uniformity of air iiow characteristics.

A further object is to provide an air conditioner utilizing a novel bafiie for controlling air ow over a heat`exchange coil and/or through a by-pass that imposes a variable resistance in the vby-pass to compensate for chan-ging resistance with change in ow over the heat-exchange coil.

A` further object is to `provide an air conditioning system utilizing .a novel by-pass flow control baffle that provides balanced Ipressure drops through the-heat-exchanger coil and by-pass passage, thereby causing substantially equal quantities of air to be delivered by the unit irrespective of the vane position, cg. of flow through the coil.

A further object is to provide an air conditioning system wherein, though air is moved through a heat-exchange coil and/or by-pass passage, the fan moving the air encounters a constant pressure drop at all times.

Other objects of this invention will appear in the following. description and appended claims, reference being had to the accompanying drawings forming a part of this specification wherein like lreference characters designate corresponding parts in the several views. A

In the drawings: FIGURE 1 is a vertical sectional view through on embodiment of air conditioner embodying the present invention;

FIGURE 2 4is a vertical sectional view through a Second embodiment of the invention;

FIGURE 3 is a .tabulation of values from FIGURE 2; and

FIGURE 4 is an illustration of a curved bale in accordance with the invention. u

Before explaining the present invention in detail, itis to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and o f being practiced or carried out in various ways. Also, it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

The environment The environmental surroundings of the present invention are typified by the showing of FIGURE 1. In this figure of the drawings, there is shown in section an air conditioner such as that adapted for a room air conditioning. This unit comprises a surrounding casing 10 which includes a front wall 12, a side wall 14 and a rear wall 16. A top wall 18 interconnects the front and rear walls 12 and 14. The top wall 18 is provided with an opening 20 therein for outlet air to be moved into the room. At the bottom, though not shown, a simil-ar opening is provided to pick up air from the oor and -move it over a conditioning coil contained within the housing 10.

The rear wall 16 is of doubled, hollow structure to rcduce the heat transfer during the heating cycle, to an adjacent wall against which the unit is placed. Also, the top wall 18 is of double construction to reduce heat transfer when the unit is on the heating cycle to avoid any possibility of burns.

Positioned at the bottom within the casing 10 is a centrifugal fan assembly c-omprising a scroll-shaped housing 22 having an air opening 24 in a side wall. A fan discharge opening 26 is provided at the top. A cylindrical, vaned rotor 28 is mounted within the housing 22 to drive air from the inlet opening 24 out of the discharge opening 26. A suitable drive means including a motor not shown is mounted in the bottom of the easing 10 to propel the fan.

Positioned above the fan is the heat-exchange coil 30 comprising a plurality of horizontally disposed heat-exchange tubes 32 having fins 34 connected in heat-exchange relation. Tubes 32 are interconnected at the ends by means of U-bends, not shown; this provides a continuous circuit through the coil.' The interconnected tubes 32 form a bundle to accommodate hot water or steam for heating in winter or cool water for the cooling cycle in summer. Appropriate inlet and outlet connections are provided, not shown, to connect with a suitable heating or cooling source.

Below the coil 30 is provided a drain pan 36 to catch condensation when the unit is on the cooling cycle. This cooperates with a front inclined sub-wall 38 that helps to direct air after passage through the coils up to the outlet opening 20.

The coil 30 and pan 36 are spaced forwardly ofthe back wall 16 to provide a by-passage 40 around the coil. By

directing selected amounts of air from the fan through the` coil and/or by-pass, theytemperature of the effluent air can be controlled within desired limits.

In so operating, of course, it is desirable that the air flow from the outlet 20 remain substantially constant, so as to avoid gusts or bursts of air as variable quantities are directed through the heat-exchange coil or by-pass by thermostatic adjustment of the by-pass.4

3 The embodiment of FIGURE I As is known, the pressure drop through a coil varies with tlow. Thus, at higher ow, a greater pressure drop; and at lower flow, a lesser pressure drop. 1t follows, therefore, that a resistance of variable nutrire must be placed in the by-pass passage to render the ow through the unit constant. It will be evident from the foregoing that the prior art fiat dampers have not achieved a constant ow because of failure to allow for this factor.

To provide constant ow, therefore, the total resistance through the unit must remain constant (and equal to full flow through the coil) for all positions of the damper. In view of the fact that the resistance of the coil changes exponentially (approximately the square of the c.f.m. change), the resistance of the by-pass passage should complement the changing coil resistance and the resistance through the opening to the coil to provide the constant total resistance. Hence the area of opening, or the rate of area change provided by the leading edge of the damper with respect to the area of the by-pass passage is made to be an exponential function of the c.f.m. change. y

The control damper This is designated in FIGURE l by the reference numeral 42. In this embodiment of the invention, this element, is of generally arcuate configuration in profile but for practical purposes is made in a bending operation to include three interconnected planar portions or surfaces of particular conguration and placement relative to one another to impose changing resistance in the bypass passage as will become apparent.

Before describing the particular relationship of the planar portions, it is pertinent to point out that a pivot shaft 44 is provided adjacent the upper rear edge of the coil 30. "the top edge of the damper 42 is rolled over to fit around the shaft 44 to provide a pivotal, suspended connection.

The control baffle is moved to its varied adjusted positions by means of a lever 46 fixed a`f"6ne end on a control shaft 48. The other end of the lever 46 is pivoted to a link 50, in turn pivotally connectenl fo a bracket 52 fastened to a front, lower portion of the control damper 42. A thermostatcally controlled motor is used to set the damper 42 through the control shaft 48, lever 46, link 50 and bracket S2. "ila: arrangement is such that when the thermostat calls for treated air. the control shaft 48 rotates clockwise to move the vat f?. toward the full line position shown. This dite-tt` vgreater quantities of air through the coil 30. Wins. due to thepsoduction of -suicient treated air, the thermostat is satisfied, the control `motor is reversed ,wherebyy shaft 44 is rotated counterclockwise to move the battle 42 toward one of the dotted lino positions shown. /ts a usual thing, movement will take place in a relatively narrow range because of the tact that the room temperature is usually kept constant within about 3 to 5 degrees. This will about balance the regulated output from the coil 30.

particular baffle pro/ile The particuiar configuration of thefby-pass bafie of this embodiment of the invention comprises a top-most planar portion 54 that extends in sloping manner toward the rear of the unit, viewing the baille in full by-pass position. This planar portion terminates at a point or line 56.

Note that the planar portion 54 blends at the line 56 with a second planar portion 58 that extends downwardly toward the rear of the unit to a point or line 60. At the line 60, there is a blend to a third planar portion 62 that slopes more sharply downwardly to close against the back wall 16 at the point V, for full coil throughput. In the closed position of I, this portion 62 extends to the front and closes the coil, providing full by-pass. Also, note in position I that portion 58 actually slopes to the front of the unit.

By viewing position I, it will be noted that line 56 projects further into by-pass passage 40 than does line 60. It thus imposes greatest resistance when the baffle is in position I. This restriction is gradually and smoothly increased as the damper is opened to admit increasing amounts of ow through the coil. However, the throat of the by-pass passage is not reduced in area as rapidly as the air ow through the by-pass passage is reduced. This results in the effective resistance of the by-pass passage being reduced at the same rate as the resistance through the heat-exchange passage is increased to thus maintain the total resistance through the unit a constant.

It will be obvious as the description progresses that the line 60 takes over as the line 56 phases out (and vice7 versa) to smoothly decrease the size of the by-pass throat as the by-pass flow diminishes.

From FIGURE 1, it will be noted that tive dilfcrent positions of the baille are illustrated as follows. In considering the illustrated arrangements, it will be understood that constant volumetric flow delivery will be maintained at all vane positions because the resistance to ow is maintained the same at all positions.

Position 1.-This is the full by-pass flow position, with the coil closed. It is-at this position that the projection 56 imposes in the by-pass passage 40 a restriction equal to full flow through the coil. Therefore, a flow through the by-pass is established that will be the same as that through the coil at the full coil open position.

The proportion of restriction is represented by the ratio of the full width of the fan discharge opening 26 or O1 to the full by-pass throat width T1. This is a 65/25 ratio or a 2.6 ratio.

Position II is a partial through coil position. It will be noted that there is still a substantial restriction in the bypass passage produced by the Aprojection 56 but that the ratio is decreased to compensate for the reduced ow. This ratio is represented by 02/ T 2 which is about 48 to 20 ratio, 2.4, slightly lower than the position I. As the discussion develops, it will be noted that the ratio becomes smaller and smaller. Thus, a smooth, decrease in size is effected in the by-pass throat to compensate for de creasing flow but at an exponential rate with respect to the reduction in air tiow therethrough equivalent to the reverse of the exponential rate of increase of the resistance through the heat-exchange passage.

Throughout this discussion, it will be noted that the leading edge of the damper 42 provides, with the coil, a sum total resistance that is always equal to full flow through the coil.

Position IIL-This is substantially a one-half by-pass position and a one-half through the coil position, where the protrusion 60 has just taken over as the protrusion 56 has phased out.

Note now that the ratio is O3/T3 or 33/14 or 2.3 and has very slightly decreased to compensate for the slight decrease of flow.

Position 1V.-This is the one-quarter by-pass threequarter through coil position and the secondary protrusion continues its job previously taken over of providing a restriction in the by-pass. The ratio here is 04/74 or a 16 to 8 or 2.0.

To sum up, the ratios from the foregoing positions are tabulated as follows to show that as the ow through the by-pass decreases, the effective resistance of the by-pass passage decreases exponentially:

, Position I: /25=2.6

Position lI: 48/20=2.4 Position III: 33/l4=2.3 Position IV: 16/8=2.0

Position V is the full through coil position. At this position the resistance of the coil is the total resistance and as has been pointed out before, this has been the ef- .fective amount ofthe resistance through the unit throughthroat has been a logarithmic type function, effected al-iy most as smoothly as though the baille profile were a curve' drawn through the points 56 and 60 and the leading and trailing edges of the baille.v It could thereforev well-be argued that the restriction in the by-pass passage varies on an inverse logarithmic curve.

The embodiment of FIGURE 2 In this figure of the drawing, there is illustrated a more practical version of the invention and, as will be noted from close inspection, the bottom protrusion is the more predominant as contrasted to FIGURE 1. Thus, the bottom protrusion designated by the reference numeral 64 is controlling throughout the full range of movement of the baille. Due to the different sha-pe of the baille, it is designated by the reference numeral 66 and comprises an upper planar portion 68, generally similar to the same element 54 of FIGURE l, but more sharply downwardly sloping. At the point or line 70, the upper portion 68 blends to a second planar portion 72 also of downwardly and slightly rearwardly sloping configuration as distinguished from the section 58 of position I of FIG- URE 1, which slopes to the front. At the bottom protrusion 64, a blend is made with a forward projection 74, analogous to section 62 of FIGURE 1, position I.

' From the foregoing, it will be noted that the projection 64, the lower projection, is at all times controlling, because the upper projection 70 is never directly eX- posed in the air stream. The purpose of projection 70 is to smooth air flow and reduce turbulence. Such would be the result if projection 64 were sharp or formed as by j Logical extension and gene/al discussion By reference to FIGURE 4 it will be evident and understood that the scope of invention can be extended to include a by-pass baille of smooth and continuous curvature. Thus, analogous to a smooth curve struck substantially through the points 44, 70, 64 and 36 of FIGURE 2. A similar curve could be struck through the pertinent points of FIGURE 1.

Thus the scope of invention would include a curved baille defining agenerally convex surface to extend into the 'oy-pass passage rearwardly of the free edge to produce a variable resistance therein commensurate with the position of the damper.

As a general note, it will be evident from the foregoing description that, theoretically and actually, the invention encompasses one or more points on a control baille, moving on a radius of a circle. Also, a baille tip works on an are to provide a varying resistance of ilow therepast. It will be noted that both or all of these points function to produce a by-pass passage that is variable in its capacity but always presents, along with the heat-exchange passage, a constant resistance to flow at any flow level.

From the foregoing, it will be evident that the two passages always (e.g., at any baille position) present the same combined resistance which is equal to the maximum resistance of the coil.

Having thus described my invention, I claimzi 1. In an air conditioner, a housing defining an air ilow duct having an inlet opening and an outlet opening, means for moving air into said inlet opening and through said duct and out of said outlet opening, a damper baille dividing said duct into a heat-exchange -passage and a bypass passage, a heat-exchanger positioned in said heatexchange passage, said heat-exchanger producing a restriction to flow against the passage of air through the heatexchange passage that varies with rate of ilow, said restriction being termed R1, said damper baille being pivotally mounted adjacent one end thereof, the free end portion of the damper baille defining the relative sizes of the inlets to the by-pass and the heat-exchange passage to proportion the air flow through the duct between said passages, the free end portion of the damper baille and one wall portion of the air flow duct defining a variable restriction in the heat-exchange passage, this restriction being termed R2, said damper baille having a generally convex surface in said by-pass passage, an intermediate portion of the convex surface of the damper baille between the ends of the baille and another wall portion of the air flow duct defining a variable restriction in said by-pass passage, this restriction being termed R3, said intermediate convex portion of the damper baille being angularly spaced apart, with respect to the pivot point of the baille, from said free end portion to be closer to said other wall -portion of the air flow duct than is said free end portion for almost all positions of the damper baille, said intermediate convex portion being of substantially less extent than is the portion of the damper baffle extending therefrom to the free end of the baille, said angular spacing and the relative distances from said pivot point of the intermediate convex portion and free end portion being configured for all positions of the damper baille so that the resistance to air flow through the air flow duct is substantially a constant from the combined effects of the restrictions R1, R2 and R3.

2. In an air conditioner, a housing defining an air flow duct having an inlet opening and an outlet opening, means for moving air into said inlet opening and through said duct and out of said outlet opening, a damper baille dividing said duct into a heat-exchange passage and a bypass passage, a heat-exchanger positioned in said heatexchange passage, said heat-exchanger producing a restriction to How against the passage of air through the heatexchange passage that varies with rate of ilow, said restriction being termed R1, said damper baille being pivotally mounted adjacent one end thereof, the free end portion of the damper baille defining the relative sizes of the inlets to the by-pass passage and the heat-exchange passage to proportion the air flow through the duct between said passages, the free end portion of the damper baille and one wall portion of the air flow duct defining a variable restriction in the heat-exchange passage, this restriction being termed R2, said damper baille having a generally convex surface in said by-pass passage, said convex surface comprising a first, second and third planar surfaces angularly inclined with respect to each other, the first and second surfaces merging along a line forming a first projection that defines, with another wall portion of the damper, the narrowest restriction through the by-pnss passage when the damper baille is positioned towards full by-pass position, said second and third planar surfaces merging along a line forming a second projection that defines with said other wall portion Iof" the duct, the nnrrowest restriction in the by-pnss passage when the damper baille is positioned towards the zero by-pass position, the narrowest restrictions of said first and second projections being termed R3, said first and second projections being angularly spaced apart, with -respect to the pivot point of the baille, from said free end portion of the baille to be closer to said other wall portion of the air flow duct than is said free end portion for almost all positions of the damper baille, the distance between said first and second projections being of substantially less extent than the distance between said second projection and the free end of the baille, said angular spacing and the relative distances from said pivot point of said first and second projections and the free end portion of the baille being configured for all positionsof the damper bafiie so that the ,resistance to air flow through the `air flow duct is substantially a constant from the combined effects of the restrictions R1, R2, and R3- I 3, In an air conditioner, a housing defining an tir tlow duct having an inlet opening and an outlet opening; means for moving air into said inlet opening and through said duct and out of said outlet opening, a damper baffle dividing said duct into a heat-exchange passage and a by-pass passage, a heat-exchanger positioned in said heat-exchange passage, said heat-exchanger producing a restriction to ow againstthe passage of air through the heat-exchange passage that varies with the rate of ow, said restriction being termed R1, said damper baie being pivotally mounted adjacent one end thereof,- the free end portion of the damper baie defining the relative sizes of the inlets to first, second and third surfaces angularly arranged with `.respect to each other, the second and third surfaces mergmg along aline defining a projection, said projection and another wall portion of the air flow duct defining a variable restriction in' said by-pass passage, this restriction being termed R3, said projection being angularly 4spaced apart,

with respect to the pivot point of the baffle, .from said free end portion to be closer to said other wall portion ofthe air ow duct than is said free end portion for almost all positions of the damper bafiic, said general convex surface being'of substantially less extent than is the portion of the damper batiie extending therefrom to the free end of the bafiie, said angular spacing and the relative distances fromsaid pivot point ofthe projection and free end portion being configured for, all-positions of the damper bafiie so that the resistance to air flow through the air flow duct is substantially a constant from the combined effects of the restrictions Ri, R2, and R3..

References Cited by the Examiner UNITED STATES PATENTS 1,719,659 7/1929 Hopkins 165-54 1,876,547 9/1932 Ashley 165-103 2,147,283 2/1939 Covell 165-86 2,212,343 8/ 1940 Goehring. 2,720,151 10/1955 Kreuttner 98-38 2,806,675 9/ 1957 Conradi 165--59 X j FOREIGN PATENTS 379,663 9/ 1932 Great Britain. 686,064 1/ 1953 Great Britain.

ALDEN D. STEWART, Primary Examiner.

WILLIAM F. ODEA, Assistant Examiner. 

1. IN AN AIR CONDITIONER, A HOUSING DEFINING AN AIR FLOW DUCT HAVING AN INLET OPENING AND AN OUTLET OPENING, MEANS FOR MOVING AIR INTO SAID INLET OPENING AND THROUGH SAID DUCT AND OUT OF SAID OUTLET OPENING, A DAMPER BAFFLE DIVIDING SAID DUCT INTO A HEAT-EXCHANGE PASSAGE AND A BYPASS PASSAGE, SAID HEAT-EXCHANGER POSITIONED IN SAID HEATEXCHANGE PASSAGE, SAID HEAT-EXCHANGER PRODUCING A RESTRICTION TO FLOW AGAINST THE PASSAGE OF AIR THROUGH THE HEATEXCHANGE PASSAGE THAT VARIES WITH RATE OF FLOW, SAID RESTRICTION BEING TERMED R1, SAID DAMPER BAFFLE BEING PIVOTALLY MOUNTED ADJACENT ONE END THEREOF, THE FREE END PORTION OF THE DAMPER BAFFLE DEFINING THE RELATIVE SIZES OF THE INLETS TO THE BY-PASS AND THE HEAT-EXCHANGE PASSAGE TO PROPORTION THE AIR FLOW THROUGH THE DUCT BETWEEN SAID PASSAGES, THE FREE END PORTION OF THE DAMPER BAFFLE AND ONE WALL PORTION OF THE AIR FLOW DUCT DEFINING A VARIABLE RESTRICTION IN THE HEAT-EXCHANGE PASSAGE, THIS RESTRICTION BEING TERMED R2, SAID DAMPER BAFFLE HAVING A GENERALLY CONVEX SURFACE IN SAID BY-PASS PASSAGE, AN INTERMEDIATE PORTION OF THE CONVEX SURFACE OF THE DAMPER BAFFLE BETWEEN THE ENDS OF THE BAFFLE AND ANOTHER WALL PORTION OF THE AIR FLOW DUCT DEFINING A VARIABLE RESTRICTION IN SAID BY-PASS PASSAGE, THIS RESTRICTION BEING TERMED R3, SAID INTERMEDIATE CONVEX PORTION OF THE DAMPER BAFFLE BEING ANGULARLY SPACED APART, WITH RESPECT TO THE PIVOT POINT OF THE BAFFLE, FROM SAID FREE END PORTION TO BE CLOSER TO SAID OTHER WALL PORTION OF THE AIR FLOW DUCT THAN IS SAID FREE END PORTION FOR ALMOST ALL POSITIONS OF THE DAMPER BAFFLE, SAID INTERMEDIATE CONVEX PORTION BEING OF SUBSTANTIALLY LESS EXTENT THAN IS THE PORTION OF THE DAMPER BAFFLE EXTENDING THEREFROM TO THE FREE END OF THE BAFFLE, SAID ANGULAR SPACING AND THE RELATIVE DISTANCES FROM SAID PIVOT POINT OF THE INTERMEDIATE CONVEX PORTION AND FREE END PORTION BEING CONFIGURED FOR ALL POSITIONS OF THE DAMPER BAFFLE SO THAT THE RESISTANCE TO AIR FLOW THROUGH THE AIR FLOW DUCT IS SUBSTANTIALLY A CONSTANT FROM THE COMBINED EFFECTS OF THE RESTRICTIONS R1, R2 AND R3. 